(1) Field of the Invention
The present invention relates to a method and an apparatus for assuring working safety. More particularly, this invention pertains to a method and an apparatus which can surely provide safe work environments for workers.
(2) Description of the Related Art
For installations involving a working system which permits a movable section of a machine and men to work cooperatively, such as gas facilities which include the possibility of an explosion, it is extremely important to maintain safety measures for the workers.
When men and machines alternately work in a common work space, accidents may occur when the movable sections of a machine collide with part of a worker's body or the machine's electric power is transmitted to a worker's body. For example, in the case where a man carries work in the work space and a robot processes it, an accident is likely to occur when the arm of the robot hits against part of the man's body.
A typical conventional safety assuring system for use in such a working system is designed in such a way that an optical signal from an optical radar sensor is emanated onto the working area of the movable section of a machine, and any work involving the movable section of the machine will be stopped when the optical signal is reflected by a worker and received by the sensor, which indicates the presence of a dangerous environment. That is, the conventional safety assuring system is realized based on the concept that work on the machine side should be terminated upon detection of a dangerous condition or environment (man or men present in the work space).
With the use of such a conventional safety system, however, when the signal-emitting section of the optical radar sensor fails for some reasons and no optical signal is sent to the working area, the optical signal will not be received even if a worker or workers are in the working area of the movable section of a machine. In this case a problem in that the erroneous determination that no workers are present is made, so that the work of the machine's movable section continues, resulting in a dangerous condition. In other words, there are some situations which the conventional safety systems cannot cope with to provide safe work environments for workers.